There is much debate over the source of bromine radicals in the atmosphere that drives polar boundary layer ozone depletion events (ODEs), but there is strong evidence to suggest a source associated with the sea ice zone. Here we report the first high temporal resolution measurements of Br₂, BrCl and BrO in coastal Antarctica, made using a Chemical Ionisation Mass Spectrometer (CIMS). Mixing ratios ranged from instrumental detection limits to 13 pptv for BrO, 45 pptv for Br₂, and 6 pptv for BrCl. We find evidence for blowing snow as a source of reactive bromine both directly during a storm and subsequently from recycling of bromide deposited on the continental snowpack. An unusual event of trans-continental air mass transport might have been responsible for severe surface ozone depletion observed at Halley. The halogen source region was the Bellingshausen Sea, to the west of the Antarctic Peninsula, the air mass having spent 3 1/2 days in complete darkness prior to arrival at Halley. We, further, identify an artefact in daytime BrCl measurements arising from conversion of HOBr, similar to that already identified for CIMS observations of Br₂. Model calculations using the MISTRA 0-D model suggest a 50–60% conversion of HOBr to Br₂, and 5–10% conversion to BrCl. Careful data filtering enabled us to use the halogen observations, in conjunction with the MISTRA model, to explore the temperature dependence of the Br₂:BrCl ratio. We find evidence of a ratio shift towards Br₂ at temperatures below ~−21 °C, suggesting a relationship with hydrohalite (NaCl.2H₂O) precipitation. This suite of Antarctic data provides the first analogue to similar measurements made in the Arctic.